Unidirectional heat pump system



United States Patent 3,421,339 UNIDIRECTIONAL HEAT PUMP SYSTEM Rodney H.Volk, La Crescent, Minn., and David J. Reiste, Onalaska, Wis., assignorsto The Trane Company, La Crosse, Wis., a corporation of Wisconsin FiledMay 31, 1967, Ser. No. 642,579 US. Cl. 62-459 Int. Cl. F25b 29/00; F25b27/00; F25b 1 7/06 7 Claims ABSTRACT OF THE DISCLOSURE Background of theinvention Many engine driven heat pumps using a vapor-compressionrefrigeration cycle have been devised for heating and cooling aconditioned space. Most of these systerns, however, operate to reversethe refrigerant flow during one cycle of operation or the other. Suchsystems generally employ a complicated and somewhat unreliable reversingvalve. Further, such systems present a problem in returning to thecompressor lubricating oil which has become entrained with therefrigerant. An evaporator or condenser which may be designed for goodoil return for one direction of refrigerant flow is generally ofinferior design for returning oil to the compressor under the oppositedirection of refrigerant flow.

Systems which utilize an atmospheric air heated evaporator for theheating cycle often experience too low a suction pressure for adequatecapacity.

Further, reverse cycle systems which utilize the engine as a source ofheat generally find it difiicult and complicated to utilize the engineas a heat sink.

Summary of the invention It is generally an object of the instantinvention to provide a system which obviates the above indicatedproblems. The instant invention contemplates a heat pump refrigerantsystem employing a first refrigerant circuit for cooling and a secondrefrigerant circuit for heating and a compressor means common to each ofsaid circuits. Means for transferring refrigerant charge from onecircuit to the other as required is provided.

The instant invention further contemplates a control system fordirecting refrigerant to one or the other or both of the refrigerantcircuits for heating, cooling or compensating operation as thetemperature of the space being conditioned may dictate. This inventionemploys refrigerant circuits that make it unnecessary to reverse theflow of refrigerant Within the system thereby eliminating reversingvalve means and attendant problems of oil return. Further, thisinvention includes a means for utilizing engine heat for evaporatingrefrigerant on the heating cycle thereby eliminating problems of lowsuction pressure normally associated with atmospheric air heatedevaporators.

This invention involves a refrigeration system comprising: a refrigerantcompressor; a first refrigerant condenser; a second refrigerantcondenser; a first refrigerant ice evaporator; a second refrigerantevaporator; a first refrigerant circuit serially connecting saidcompressor, said first condenser, and said first evaporator in a closedrefrigerant loop; a second refrigerant circuit serially connecting saidcompressor, said second condenser, and said second evaporator in closedrefrigerant loop; a portion of said first and second circuits at saidcompressor being common to each other; a refrigerant receiver disposedin said first circuit downstream of said first condenser and upstream ofsaid first evaporator; a heat exchange means disposed in said secondcircuit upstream of said second condenser and downstream of said commonportion of said circuit for exchanging heat from said second circuit tosaid receiver.

This invention is directed to a refrigeration system comprising: arefrigerant compressor; a first refrigerant condenser; a secondrefrigerant condenser; a first refrigerant evaporator; a secondrefrigerant evaporator; a first refrigerant circuit serially connectingsaid compressor, said first condenser, and said first evaporator in aclosed refrigerant loop; a second refrigerant circuit seriallyconnecting said compressor, said second condenser, and said secondevaporator in closed refrigerant loop; a portion of said first andsecond circuits at said compressor being common to each other; aconditioned space disposed in heat exchange relation with said firstevaporator and said second condenser; a continuously operating internalcombustion engine drivingly connected to said compressor; and controlmeans for directing refrigerant gas from the compressor through saidfirst circuit for cooling said conditioned space, for directingrefrigerant gas from said compressor through said second circuit forheating said conditioned space, and for directing refrigerant gas fromsaid compressor simultaneously through both of said first and secondcircuits for providing a minimum heat exchange with said conditionedspace.

This invention further involves a refrigeration system comprising: arefrigerant compressor; a first refrigerant condenser; a secondrefrigerant condenser; a first refrigerant evaporator; a secondrefrigerant evaporator; a first refrigerant circuit serially connectingsaid compressor, said first condenser, and said first evaporator in aclosed refrigerant loop; a second refrigerant circuit seriallyconnecting said compressor, said second condenser, and said secondevaporator in closed refrigerant loop; a portion of said first andsecond circuits at said compressor being common to each other; aninternal combustion engine drivingly connected to said compressor; meansfor cooling said engine with a cooling fluid; means for heat exchangingsaid cooling fluid with said second evaporator.

Other objects and advantages will become apparent as this specificationproceeds to describe the invention in detail with reference to theaccompanying drawings in which:

FIGURE 1 is a flow diagram of a refrigeration system incorporatingaspects of the instant invention;

FIGURE 2 is a table showing the modes of operating the system shown inFIGURE 1; and

FIGURE 3 is a temperature control. circuit for the system shown inFIGURE 1.

Now referring to FIGURE 1, it Will be seen that the refrigeration systemhas a first refrigeration circuit 1 comprising a refrigerant compressor2, a first solenoid operated normally closed shut-off valve 3, an aircooled refrigerant condenser 4, a first refrigerant receiver 5, aone-way check valve 6 arranged for fiow from the receiver, a secondsolenoid operated normally closed shutoff valve 7, a second receiver 8adapted to be heated by refrigerant in a second refrigerant circuit yetto be described, the first portion 9 of a suction line heat exchanger14, a throttling means such as thermostatically controlled expansionvalve 10, an air heated evaporator 11 disposed in heat exchange relationwith a space 12 to be temperature conditioned, and the second portion 13of heat exchanger 14 respectively serially connected in a closedrefrigerant loop. The refrigeration system further has a secondrefrigerant circuit 15 comprising compressor 2, solenoid operatednormally closed shut-off valve 16, heat exchanger 17 adapted to heatreceiver 8, an air cooled condenser 18 disposed in heat exchangerelation with space 12, a liquid-gas separator 19, a refrigerant liquidreceiver 20, a throttling means such as thermostatically controlledexpansion valve 21, and a water heated evaporator 22 respectivelyserially connected in a closed refrigerant loop. Second refrigerantcircuit 15 further includes a conduit 23 bypassing receiver 20 andexpansion valve 21 for conducting gas from separator 19 to a point inthe second refrigerant circuit downstream of expansion valve 21 andupstream of evaporator 22 which includes a thermostatically controlledvalve 24 arranged to open upon sensing a temperature below apredetermined temperature. It will be noted that those portions of saidfirst and second circuits immediately upstream and downstream ofcompressor 2 are common to each other.

Compressor 2 is driven continuously by internal combustion engine 25.Engine 25 is provided with a water cooling system including a watercirculator pump 26, a heat exchanger 27 adapted to heat evaporator 22and an air cooled engine radiator 28 respectively connected in serieswith the water jacket of engine 25. The cooling water circuit furtherhas a bypass conduit 29 shunting radiator 28 provided with a watertemperature responsive valve 35) for controlling the temperature of thewater returning to the engine. Valve 24 is arranged to be responsive tothe temperature of the water in that portion of the water coolingcircuit downstream of pump 26 and upstream of heat exchanger 27.

The refrigeration system further has a fan 31 for passing atmosphericcooling air sequentially over condenser 4 and radiator 28. Evaporator 11and condenser 18 are constructed as separate circuits in a singlefin-andtube heat exchanger 32 having common fins 33 embracing bothcircuits. Fan 34 is arranged to pass air from the conditioned space overheat exchanger 32 for conditioning the air in space 12. A controlthermostat 35 arranged in heat exchange relation with space 12 operatesthe valves 3, 7 and 16 in accordance with the operating modes shown inthe chart of FIGURE 2. The control circuit for this purpose is shown inFIGURE 3.

Operation Assume engine 25, fan 31 and fan 34 are operating and space 12is excessively warm. The bellows of temperature controller 35 is in aposition energizing solenoid valves 3 and 7 to their open position andde-energizing solenoid valve 16 to its closed position. No refrigerantflows in refrigerant circuit 15 as valve 16 is closed. Compressor 2delivers refrigerant gas under high pressure via valve 3 to condenser 4.The refrigerant is cooled and caused to condense in condenser 4 by thecooling air from fan 31. Condensed refrigerant passes to receiverthrough check valve 6, open solenoid valve 7, receiver 8 to the firstportion 9 of suction line heat exchanger 14 where the liquid refrigerantis further cooled by heat exchange with suction gas. The subcooledliquid refrigerant is throttled to a lower pressure by passage throughexpansion valve 10. The refrigerant at greatly reduced pressure iscaused to evaporate in evaporator 11 by heat absorbed from the air ofthe condition-space circulated over evaporator 11 by fan 34. Thevaporized refrigerant passes to the suction side of the compressor viathe second portion 13 of the suction line heat exchanger 14. During thiscooling cycle of operation, receiver 8 is substantially full of liquidrefrigerant. Also the engine 25 is cooled by cooling water which passesfrom pump 26,

through exchanger 27, and radiator 28 from whence it is returned to theengine. Bypass 29 and thermostatic valve 30 control the temperature ofthis return water. The system operating in this manner will cause thetemperature in conditioned space 12 to be lowered until thermostaticcontrol 35 indicates that no further substantial cooling is needed byenergizing valve 16 thus causing valve 16 to open. Valves 3 and 7 remainenergized and open.

A portion of the compressed refrigerant from compressor 2 continues topass through the first refrigerant circuit in the manner just described.However, since valve 16 is now open, a portion of the compressedrefrigerant from compressor 2 passes through valve 16, heat exchanger17, to condenser 18. The hot refrigerant gas is then cooled andcondensed by heat rejected to the conditioned space via the air directedover condenser 18 by fan 34. Also some heat is conducted directly toevaporator 11 via fins 33. The condensed refrigerant then passes throughseparator 19, receiver 20 to expansion valve 21 where the pressure isreduced upon the refrigerant entering evaporator 22. The liquidrefrigerant at reduced pressure in evaporator 22 is vaporized by heatfrom the engine cooling water in heat exchanger 27. The thus vaporizedrefrigerant is returned from evaporator 22 to compressor 2. Sinceevaporator 11 tends to cool while condenser 18 tends to heat theconditioned space, the net exchange of heat between the conditionedspace and heat exchanger 32 is little or nothing. If desired, the systemcomponents may be designed to achieve small net cooling or heating byexchanger 32 under this compensating cycle of operation.

Should the conditioned space drop in temperature sufificiently torequire heating, temperature controller 35 will further move to aposition de-energizing and opening solenoid valves 3 and 7 thusterminating flow through the first refrigerant circuit. Valve 16 remainsenergized and open and the second refrigerant circuit continues tooperate in a manner similar to that just described. However, now all thecompressed refrigerant gas from compressor 2 is directed through valve16, etc. This gas passing through heat exchanger 17 causes somerefrigerant in receiver 8 to vaporize whereupon the refrigerant inreceiver 8 is driven through evaporator 11 into the suction side of thecompressor and ultimately into the second refrigerant circuit. Thus alarge portion of the refrigerant used in the first refrigerant circuitfor the cooling cycle is utilized in the second refrigerant circuitduring the heating cycle thereby minimizing the amount of refrigerantrequired in the system.

Should the internal combustion engine 25 be first started when heatingof space 12 is required, the cooling water in heat exchanger 27 will notat first have sufficiently high temperature to vaporize the refrigerantliquid in evaporator 22. To assist in starting the refrigerant flowthrough the second refrigerant circuit, valve 24 is opened in responseto low cooling water temperature. This permits the refrigerant gas atseparator 19 to temporarily bypass receiver 20 and expansion valve 21thereby permitting an unrestricted flow of refrigerant gas back to thecompressor. Separator 19 permits substantially only gas to travel thisroute so that no slugging will occur in the compressor. After the normalengine temperatures are reached, valve 24 is closed and all refrigerantpassing through the second refrigerant circuit 15 must pass throughexpansion valve 21 as during normal operation under compensating orheating modes of operation.

Having thus described in detail the preferred embodiment of ourinvention, we contemplate that many changes may be made withoutdeparting from the scope or spirit of our invention and we accordinglydesire to be limited only by the claims.

We claim:

1. A refrigeration system comprising: a refrigerant compressor; meansfor driving said compressor; a first refrigerant condenser; a secondrefrigerant condenser; a

first refrigerant evaporator; a second refrigerant evaporator; a firstrefrigerant throttling means; a second refrigerant throttling means; afirst refrigerant circuit serially connecting said compressor, saidfirst condenser, said first refrigerant throttling means, and said firstevaporator respectively in a closed refrigerant loop; a secondrefrigerant circuit serially connecting said compressor, said secondcondenser, said second refrigerant throttling means, and said secondevaporator respectively in a closed refrigerant loop; a portion of saidfirst and second circuits at said compressor being common to each other;a refrigerant receiver disposed in said first circuit downstream of saidfirst condenser and upstream of said first evaporator; a heat exchangemeans disposed in said second circuit upstream of said second condenserand downstream of said common portion of said circuit for exchangingheat from said second circuit to said receiver.

2. The apparatus as defined by claim 1 including valve means disposed insaid first circuit downstream of said first condenser and upstream ofsaid receiver for preventing reverse flow in said first circuit whensaid receiver is heated by said heat exchange means.

3. The apparatus as defined by claim 1 including a conditioned spacedisposed in heat exchange relation with said first evaporator and saidsecond condenser; a first valve means disposed in said first circuitupstream of said first condenser and downstream of the common portion ofsaid circuits; a second valve means disposed in said first circuitupstream of said receiver and downstream of said first condenser; athird valve means in said second circuit up stream of said heat exchangemeans and downstream of the common portion of said circuits; and controlmeans for opening said first and second valve means and closing saidthird valve means for cooling said conditioned space, for closing saidfirst and second valve means and opening said third valve 'means forheating said conditioned space, and for opening said first, second andthird valve means for providing minimum heat exchange with saidconditioned space.

4. A refrigeration system comprising: a refrigerant compressor; a firstrefrigerant condenser; a second refrigerant condenser; a firstrefrigerant throttling means; a second refrigerant throttling means; afirst refrigerant evaporator; a second refrigerant evaporator; a firstrefrigerant circuit serially connecting said compressor, said firstcondenser, said first refrigerant throttling means, and said firstevaporator respectively in a closed refrigerant loop; a secondrefrigerant circuit serially connecting said compressor, said secondcondenser, said second refrigerant throttling means, and said secondevaporator respectively in a closed refrigerant loop; a portion of saidfirst and second circuits at said compressor being common to each other;a conditioned space disposed in heat exchange relation with said firstevaporator and said second condenser; a continuously operable internalcombustion engine drivingly connected to said compressor; and controlmeans for directing refrigerant gas from the compressor through saidfirst circuit for cooling said conditioned space, for directingrefrigerant gas from said compressor through said second circuit forheating said conditioned space, and for directing refrigerant gas fromsaid compressor simultaneously through both of said first and secondcircuits for providing a minimum heat exchange with said conditionedspace. '1

5. A refrigeration system comprising: a refrigerant compressor; a firstrefrigerant condenser; a second refrigerant condenser; a firstrefrigerant throttling means; a second refrigerant throttling means; afirst refrigerant evaporator; a second refrigerant evaporator; a firstrefrigerant circuit serially connecting said compressor, said firstcondenser, said first refrigerant throttling means, and said firstevaporator respectively in a closed refrigerant loop; a secondrefrigerant circuit serially connecting said compressor, said secondcondenser, said second refrigerant throttling means, and said secondevaporator respectively in a closed refrigerant loop; a portion of saidfirst and second circuits at said compressor being common to each other;an internal combustion engine drivingly connected to said compressor;means for cooling said engine with a cooling fluid; and means for heatexchanging said cooling fluid with said second evaporator.

6. The apparatus as defined by claim 5 including a gasliquid separatordisposed in said second circuit downstream of said second condenser andupstream of said second evaporator; refrigerant throttling meansdisposed in said second circuit downstream of said separator andupstream of said second evaporator; a bypass conduit connected to saidseparator for conducting gas therefrom to a point in said second circuitdownstream of said throttling means on the upstream side of said "secondevaporator; and automatic valve means in said bypass conduit responsiveto the temperature of said engine cooling fluid.

7. The apparatus as defined by claim 5 wherein said first evaporator andsaid second condenser are first and second circuits respectively of aheat exchanger having fins common to both the circuits of the heatexchanger and disposed in heat exchange relation with a conditionedspace.

References Cited UNITED STATES PATENTS 2,154,136 4/1939 Parcaro 621732,213,654 9/1940 Melcher 62--323 XR 2,291,029 7/ 1942 Everetts 621732,932,178 4/1960 Armstrong 62428 XR 3,105,366 10/1963 Atchison 62173MEYER PERLIN, Primary Examiner.

US. Cl. X.R.

